Chronic progressive heart failure will be produced in sheep by administration of specific myocardiotoxic drugs. In Phase I, project feasibility will be determined by administering allylamine, doxorubricin, or cobalt chloride in varying doses to healthy sheep, then following changes which occur with time in cardiac output, hemodynamics in the great vessels and all four chambers of the heart, and left ventricular ejection fraction determined by cineangiocardiography and echocardiography -- all determined with the animal at rest and on graded exercise. Results will be compared to recognized changes which occur in clinical patients with chronic congestive cardiomyopathic heart failure. Feasibility will be demonstrated if one or more of the drugs and dosage schedules succeeds in producing chronic heart failure in sheep which closely resembles, pathophysiologically, the clinical and pathologic picture of chronic congestive heart failure in human subjects with progressive cardiomyopathy. In Phase II of the project, drug dosage and animal management protocols will be modified and/or adjusted to optimize the clinical relevance of the animal model, and detailed functional and pathophysiologic characterization of the experimental model will be carried out. Phase III will accomplish standardization of the protocols for production and management of the model as well as its production in quantity and its commercial distribution to (and utilization by) cardiologic researchers for fundamental and applied research activities related to chronic heart failure. Production of such a model and its availability to the scientific community is an established research target of the NHLBI.